People benefit from plastic articles. From their invention in the mid-20th Century until the present, thermoplastic polymers have become the composition of many consumer products. Such products are relatively lightweight, sturdy, and corrosion resistant.
Thermoplastic polymers during the past half-century have used resins produced from petrochemical feedstocks. As this Century progresses, there will be an increasing need to produce thermoplastic polymers from biomass feedstocks, whether because of geopolitical considerations, environmental considerations, or supply considerations. One of the thermoplastic polymers produced from bio-derived sources are polyhydroxyalkanoates.
According to European Patent Publication 1 705 250, poly-hydroxyalkanoates (PHAs) are biological polyesters accumulated in cells by special microorganisms under special growth conditions and have the following general formula:
in which, n and m are integers from 1 to 4; R1 and R2 are straight chain or branched chain C1-12 alkyl which are substituted or non-substituted; X and Y are not 0 simultaneously, and determine the content of the components in copolymer. The average molecular weight of PHAs is generally 1-4 million Da.
The physical property of PHAs is similar to that of polypropylene. But because its biodegradability, biocompatibility, piezoelectricity and optical activity are characteristics not possessed by common petrochemical resins, it has wide application prospect in industry, agriculture, medicine, sanitation, food, electronics, etc.
Unfortunately, PHAs have crystallinity problems. The crystallinity of PHA increases over time, causing thermoplastic compounds made from that polymer resin to become more brittle over time of storage or use. To counter that, nucleating agents, such as boron nitride, have been used to stabilize the crystallinity creep of the PHA by causing it to crystallize to its maximum prior to commencement of storage or use. In that manner, the crystallinity of PHA can be accounted for in the engineering of physical properties of the thermoplastic compound.